As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Monday, 6 March 2017

How migratory birds respond to balmier autumns?

Study of songbird migrants
demonstrates the importance of temperature in the decision to begin migration

Date: February 22, 2017

Source: De Gruyter Open

Around the world, no matter where
we are, we can usually expect the weather to change from one season to the
next. In North America, the warm days of summer eventually turn into the cooler
days of autumn, and these changes are vital to a lot of the animals that
inhabit the region as they trigger the urge of animals to prepare for winter.
Migratory animals, like songbirds, use these predictable weather changes as
environmental cues to tell them when it's time to migrate south. But with the
earth now getting hotter and hotter each year, birds can no longer rely on the
once predictable climate. As autumns are becoming milder, ornithologists keep
pondering on how it could be affecting birds' migratory decisions. Now, a new
paper published this week in an online journal Animal Migration, has
experimentally investigated how birds use temperature as a signal to migrate.

The study led by Adrienne
Berchtold from the Advanced Facility for Avian Research at the University of
Western Ontario, focused on one songbird species that is known to rely on
weather for its migratory journey: the white-throated sparrow. The bird
migrates from Canada to the southern United States each autumn, and it tends to
migrate later than other migrants, basing its journeys on when the weather
provides opportunities for flight.

To figure out the underlying
pressures that drive the birds to migrate, the researchers captured
white-throated sparrows during one autumn migration and placed them in
specially-designed bird cages equipped with high-tech monitoring gear that kept
track of how active the birds were by day and night. The scientists then
changed the room temperatures throughout the experiment to see how the birds
would react. When the temperature dropped to chilly 4ºC, in an attempt to mimic
the typical fall conditions in the northern part of the flyway, the birds all
became restless at night, signifying they were in a migratory state. When, in
turn, the temperature was raised to a warm 24ºC, none of the birds showed signs
of migratory restlessness, indicating they were under no pressure to depart in
these balmy conditions.